A bucket-wheel excavator is a continuous-digging machine normally used in large-scale stripping and mining of brown-coal deposits. It has a boom on which is mounted a rotating vertical wheel provided on its periphery with buckets. The rotating wheel is pressed into the material to be dug so that the buckets cut, gather, and discharge material dug up onto a conveyor belt that carries it away from the excavator. Such machines have capacities as large as 200,000 m.sup.3.
The enormous bucket wheel is supported on the frame of the bucket-wheel excavator by means of a very heavy-duty bearing. This bearing is provided on the shaft assembly which extends between the bucket wheel at one end and the drive wheel at the other end, which drive wheel is normally connected by several belts or a chain to the drive motor. Due to the large size of the bucket wheel at one end and the drive wheel at the opposite end it is therefore necessary to use a split-ring bearing between these ends, as a nonsplit-ring bearing could not be fitted over the ends of the shaft assembly. This bearing is a relatively expensive and complex structure.
It has been suggested to avoid this use of a split-ring bearing by journaling the shaft assembly at several locations, and making the bucket wheel or excavator wheel removable so that the shaft can be fitted through these bearings and then have the bucket wheel or drive wheel mounted on it. Such structures themselves become relatively complex, and often create considerable problems in securing the removable wheel to the shaft, as enormous torque must be transmitted from the shaft to the wheel. These structures, which normally require bearings to be mounted on the outer ends of the shaft outside the bucket and drive wheels therefore take up considerable room and are quite expensive. Furthermore a relatively long shaft length is necessary between the drive wheel and the bucket wheel.